Fix #includes

- Where std::nullptr_t is used (in namespace std), #include <cstddef>,
   even if it appears alongside <stddef.h> because types like intptr_t
   are used (in the root namespace).
 - Where math library functions are used, #include <cmath> to get and
   use the versions of functions in namespace std which are overloaded
   by argument type, such as std::isinf and std::isnan.

third_party is excluded.

Change-Id: Ic9c143f407e5a9c5cff4098cf566ba5caf4bf6d8
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/6021439
Commit-Queue: Mark Mentovai <mark@chromium.org>
Reviewed-by: Joshua Peraza <jperaza@chromium.org>

snapshot/linux/signal_context.h

@@ -16,11 +16,11 @@
 #define CRASHPAD_SNAPSHOT_LINUX_SNAPSHOT_SIGNAL_CONTEXT_H_
 
 #include <signal.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <sys/types.h>
 #include <sys/ucontext.h>
 
-#include <cstddef>
 #include <type_traits>
 
 #include "build/build_config.h"

util/misc/from_pointer_cast.h

@@ -15,6 +15,7 @@
 #ifndef CRASHPAD_UTIL_MISC_FROM_POINTER_CAST_H_
 #define CRASHPAD_UTIL_MISC_FROM_POINTER_CAST_H_
 
+#include <stddef.h>
 #include <stdint.h>
 
 #include <cstddef>

util/synchronization/semaphore_posix.cc

@@ -15,10 +15,10 @@
 #include "util/synchronization/semaphore.h"
 
 #include <errno.h>
-#include <math.h>
 #include <time.h>
 
 #include <chrono>
+#include <cmath>
 
 #include "base/check_op.h"
 #include "base/logging.h"
@@ -43,7 +43,7 @@ void Semaphore::Wait() {
 bool Semaphore::TimedWait(double seconds) {
   DCHECK_GE(seconds, 0.0);
 
-  if (isinf(seconds)) {
+  if (std::isinf(seconds)) {
     Wait();
     return true;
   }
@@ -81,7 +81,7 @@ void Semaphore::Wait() {
 bool Semaphore::TimedWait(double seconds) {
   DCHECK_GE(seconds, 0.0);
 
-  if (isinf(seconds)) {
+  if (std::isinf(seconds)) {
     Wait();
     return true;
   }